Method of burning fuel



Patented June 11, 1929.

UNITED STATES THOMAS M. CHANCE, OF MERION, PENNSYLVANIA.

METHOD OF BURNING FUEL.

No Drawing.

My invention relates to the burning or combustion of fuels in which difficulty is occasioned by the clinkering of the ash and has for its object the reduction in, or the removal of, the difficulty occasioned by clinkering. I attain this end by mixing with the fuel a non-clinkering substance, or one in which clinkering can only occur at relatively high temperatures. If to a coal in which clinke"- ing is troublesome, there be added a relatively infusible or difficultly fusible material such for example as fireclay, reduction in clinkering difficulties will be effected either by the isolation of each particle of coal, whereby the clinkers formed by each particle are distributed through the infusible material, or by the admixture of the ash of the coal with the fireclay whereby the fusion temperature of the mixture is increased to one greater than the fusion temperature of the ash alone. If the coal and fireclay are both in finely divided form, that is, in relatively small particles, such intimate admixture of the ash and tireclay may produce such increase in the fusion temperature of the mixture above that of the ash of the coal, whereas if the particles of coal are large, while the ash of each particle may become fused and form a clinker, the clinkers formed by the different pieces of coal will be prevented from running together to form large clinkers by the presence of fireclay which tends to isolate the coal clinkers and prevent them from agglomerating.

In carrying out my invention it will often be possible to recover such iireclay or other diificultly fusible material from the ash and clinkers mixed therethrough, by screening, the liner particles of fircclay' and diflicultly fusible particles of the coal ash being thus recovered for reuse.

In the operation of power plants combustion must be forced during peak hours of the load, and during such hours the temperature of the fuel bed is much higher than when operating at normal or average rate. Hence many coals which can be used without trouble from clinkering under normal conditions clinker badly under peak load conditions. As the fusibility of the ash in the individual particles of coal comprising the fuel bed may vary widely, some particles having relatively high fusion temperature of the ash while other particles have relatively low fusion temperature, large masses of clinker often contain more or less unfused ash from those particles of coal with difficultly fusible ash,the

Application filed February 1, 1927. Serial No. 165,248.

ashes as drawn from the ash pit consisting of a mixture of clinkers and finely divided ash which has not been fused. This unfused ash may be screened from the clinkered ash, and used as a diflicultly fusible material to mix with the coal, to prevent or reduce the clinkering tendency under peak load conditions. The advantage in carrying out this special method of applying my invention is of course in the economy and convenience of obtaining the inert refractory material directly from the ashes.

When the ash of the coal is all, or nearly all, of relatively low fusion temperature, and the ashes furnish little unfused material, this may be supplied by mixing with the coal a sufficient quantity of coal having a difficul-tly fusible ash, the unfused portion being recovered from the ashes and mixed with the coal as already described. The mixing of coals to reduce the tendency to clinkering has been practiced, and I do not claim admixture for this purpose except in combination with recovery of unfused ash and admixture thereof with the coal.

High fusion temperature of ash is usually intended to mean 2600 Fahr. to 3000, or more, Fahn, and low fusion temperature to mean about 2200" or less Fahr., temperatures from 2.200 Fahr. to 2600 Fahr. being classed as average, or moderate fusibility.

The cause of clinking in coals with normally high fusion temperature is usually attributcd to the presence of iron existing as iron pyrites (FeS,) commonly spoken of as sulphur. As the distribution of pyrite throughout the individual layers or benches of coal beds, or throughout any single layer or bench, is quite irregular, some pieces of the coal as mined may contain very little pyrite while other pieces contain pyrite in concentrated or segregated form, the difference in fusibility of the ash of different pieces or par ticles of coal is readily understood. Similar variations in fusibility may be caused by varying quantities of lime, magnesia, alumina and the alkalies in the ash.

The mixing of powdered coal with powdered material having high chemical affinity for the ash of said coal to insure chemical union between said ash said added material and thus to so change the chemical composition of a clinkering ash and produce a nonadherent resultant clinker is known, and I therefore limit the scope of my invention to the admixture of coal with refractory materials that are relatively chemically inert to the ash of said coal and whiehproducc the desired results by mass action and by physical isolation of the individual masses of fusible clinker.

In this specification and the claims hereof the words coal and fuel are used interchangeably to mean and to include any material such coke, coke breeze, charcoal, etc. used as fuel in which the admixture of a dilticultly fusible substance will reduce or eliminate clinke'ring or fusion of the ash.

Having described my invention, I claim:

. 1. A method of burning coal which consists in admixing therewith unfused portions of the ash of said coal, in burning said mixture,in recoveringfrom the ashes of said mixture unfused portions of said ash and in mixing said unfused portions with coal, whereby unfused portions of the ash are returned in closed circuit of operation for reuse to reduce the tendency to clinkering.

2. A method of burning coal having ash of relatively low fusion temperature which consists in mixing said coal with coal having ash of relatively high fusion temperature, in burning said mixture, in recovering from the ashes of said mixture, unfused portions thereof and in mixing said unfused portions with said mixture, in recovering unfused portions of the ash of said mixture for reuse, whereby the quantity of coal having high fusion temperature necessary to mix with said coal having low fusion temperature can be reduced to that required to make up the unavoidable loss of unfused portions of the ash.

Signed at Philadelphia, Pennsylvania, this 

